President Barack Obama does the 'Gator Chomp' as he walks into Gator's Dockside to greet patrons during an unschedule stop, Saturday, Sept. 8, 2012, in Orlando, Fla. (AP Photo/Pablo Martinez Monsivais)

ORLANDO, Fla. (AP) — President Barack Obama is unleashing a new Medicare offensive against rival Mitt Romney, eager to shake his Republican challenger off his economic focus and turn the campaign on to territory more favorable to Democrats.

Campaigning for a second day in Florida, where older voters and workers approaching retirement hold sway, Obama on Sunday was expected to highlight a study by a Democratic leaning group that concluded that on average a man or woman retiring at age 65 in 2023, would have to pay $59,500 more for health care over the length of their retirement under Romney's plan.

The numbers are even higher for younger Americans who retire later, the study found. A person who qualifies for Medicare n 2030 — today's 48-year-old — would see an increase of $124,600 in Medicare costs over their retirement period.

The study was conducted by David Cutler, a Harvard professor and health policy expert who served in the Clinton administration and was Obama's top health care adviser during the 2008 presidential campaign. Cutler conducted the study for the liberal Center for American Progress Action Fund.

A senior administration official said Obama would draw attention to the study on Sunday as he takes his two-day Florida bus tour to Melbourne and West Palm Beach on Florida's Atlantic Coast.

Romney would seek to contain Medicare costs by giving retirees voucher-like government payments that they could use to either buy regular Medicare or private health insurance. But Cutler says older Americans would have to pay more out of pocket to cover the rising costs of health care.

Obama aides believe they successfully forced Romney to temporarily drop his emphasis on the sluggish economy last month by raising the Medicare issue in the wake of Romney's selection of Rep. Paul Ryan as his running mate. Romney and Ryan countered by arguing that Obama planned to cut hundreds of billions of dollars in Medicare spending over 10 years to pay for his health care plan.

Whether either side gained politically from that debate is unclear. But Republican analysts say it did take Romney off his economic focus, which they say is essential for him to win the election, especially after a bleak jobs report that showed meager job growth and more unemployed people choosing not to seek work.

Campaigning in Kissimmee, Fla., on Saturday, Obama had already worked Medicare into rally speeches.

"I want you to know I will never turn Medicare into a voucher," he told a high energy crowd of 3,000 at the Kissimmee Civic Center. "I believe no American should ever have to spend their golden years at the mercy of insurance companies. After a lifetime of labor, you should retire with dignity and respect."

Vice President Joe Biden, campaigning in Ohio, called the GOP plan "Vouchercare."

Biden said the Romney and Ryan plan would force "Mom" to go out into the insurance market and look for the best deal she can find. If the plan costs more than the voucher amount, "They say, 'Mom go borrow somewhere' " to pay for it, Biden said.

Cutler's Democratic affiliations make him vulnerable to accusations of partisanship. But much of his data is drawn from studies by the independent Congressional Budget Office, which has projected even higher costs to future retirees under a 2011 budget plan written by Ryan, a Wisconsin Republican who chairs the House Budget Committee.

The budget agency said future retirees would pay more under Ryan's plan than if they went into traditional Medicare. By 2030, a typical 65-year-old would be paying two-thirds of his or her health costs, the agency said.

Romney spokeswoman Amanda Henneberg said the vice president's comments were "further proof that the Obama campaign is unable and unwilling to talk honestly or substantively about the most important issues driving the country."

Romney and Ryan were planning to be off the campaign trail Sunday, although both men taped appearances on several Sunday talk shows.

As the campaign moves into its post-convention frenetic pace, the Obama campaign also began to tar Romney with guilt by association, accusing him of embracing extreme partisan policies.

The campaign accused Romney of not standing up to "the most strident voices in his party" because he acknowledged Rep. Steve King at an Iowa rally. King is a conservative congressman from Iowa who has taken tough anti-immigration stances, including suggesting an electrified fence along the Mexican border.

"This man needs to be your congressman again," Romney said at an event Friday. "I want him as my partner in Washington D.C."

The Democratic National Committee followed with a Web video Saturday that concluded in bold letters: "Mitt Romney & Steve King. Partners in extremism."

Romney spokesman Kevin Madden brushed aside the criticism. King "has been supportive of the governor and he's come to a number of our events in the past," Madden told reporters.

The Obama camp again accused Romney of "associating with some of the most strident and divisive voices in the Republican Party," after a Romney aide told reporters that the GOP nominee "spoke briefly" with conservative televangelist Pat Robertson at a campaign event on Saturday.